SonexBuilders.net

I have been flying my Sonex about 10 years with 485 hours on her and I have recently had accuracy problems with my Airspeed Indicator. Several months ago it started reading about 5 to 10 mph low (from CAS). More recently it started reading up to 40 mph low. :o I discovered the cause was both my pitot and static lines in the wing had some kind of fluid in them. Not water, it looks like some kind of oil based fluid - slightly yellow. Even the outside of the lines had a light film on them.

The plane has always been hangered and no fluids of any kind have ever been near the lines. The lines are yellow Tygon Tubing and I think I purchased them from Aircraft Spruce (11 years ago). Anyone seen this before? Any ideas?

Bob Sonex 550 Jabiru 2200 485 hours

Bob, I purchased my kit second hand and it included that same yellow tygon tubing unused in a plastic bag. It was covered in a yellow oil like substance. It was about 8 years since the original owner purchased it. I threw it out and bought new clear tygon.

Sounds like my problem. Thanks.
Bob

After flying my Sonex for almost 10 years, I had the same problem with oily fluid in my pitot line. I blew it out and was good for another year, then had to do it again.

I received the yellow tygon tubing with my Sonex kit purchased in 2007. When I went to install the pitot system in 2014 I had the same oily substance inside & outside my tubing. I think the stuff just degrades and turns to oil so I considered it unusable, threw it away and installed new clear tubing - I was a bit annoyed as the tubing was all neatly plumbed into place through bushings in every wing rib, and the wings were attached and rigged. I had to make a flush connector so I could draw the new lines through the rib bushings - no problems with airspeed/altimeter after new install.